A related release notes item, in the 'DEPLOYMENT NOTES AND KNOWN ISSUES' section, states:

wns0008309Under certain low signal conditions or areas of high data traffic,iPad's running IOS 5.1.1 or later could disconnect from the networkrandomly. This issue seems to be device and OS specific. Enterasys willcontinue investigating this problem to identify the root cause andpropose potential solutions. The issue has not been replicated on otherOSes or platforms at this time.

SolutionUpgrade the controller to the next firmware release (8.11.08.0002 or 8.21.02.0063), or higher.Release notes state, in the 'Changes in 8.11.08.0002' section:wns0008309Corrects issue with ipad2 using iOS v6.0.1 getting deauthed from ap running v8.11.07.0007Release notes state, in the 'Changes in 8.21.02.0063' section:wns0008309Corrects issue with ipad2 using iOS v6.0.1 getting deauthed from ap running v8.11.06.0013